There are many ion exchange (“IX”) metathesis processes used commercially. Current commercial processes exchange univalent ions with other univalent ions or divalent ions with other divalent ions to generate their metathesis products. None of these processes are useful for high concentration cation exchange of univalent ions with divalent ions to produce both high concentration univalent and divalent salt products.
In typical water softening applications, where hardness minerals are removed from aqueous streams using cation exchange media, regeneration, typically using sodium chloride or hydrochloric acid, uses relatively large stoichiometric excesses of the regenerating ions. For example, sodium chloride regeneration is often applied at 2.5 times the resin active capacity. The cost of the excess required reagent NaCl is typically not recovered and results in an effluent stream from the IX regeneration process that typically consists of a non-useful mixture of univalent and divalent counter ions (e.g., Na+ and Ca++). The spent regenerating solution is typically of no value and must be disposed of at some additional cost. The typical regeneration effluent normally leaves the process at relatively lower concentrations and naturally translates to large volumes of waste brine that further serves to increase operating costs.
Other commercial ion exchange metathesis processes exchange univalent ions, such as Na+, H+, and K+, making the requirements for resin selection and operating conditions for such processes less demanding. These processes include: the Mono-Potassium Phosphate process (H+ exchange with K+ to give KH2PO4), the Vicksburg Chemical “K-Garb” Process (NH4+ with K+ to give K2CO3), the Nalco Silicic Acid Production (Na+ with H+ to give H2SiO3), and the Potassium Nitrate/HCl Production Process (exchanging H+ with K+ to give KNO3).
Other IX metathesis processes, such as described in U.S. Pat. No. 6,649,136 have been proposed for commercial preparation of a sodium cyanide product from a calcium cyanide feed along with a high purity calcium chloride product from the sodium chloride regeneration process. This and allied processes require a process design and operating methodology that allows both high concentration and high purity for each IX effluent (product) stream. The current invention provides a means of selecting the optimum resin and operating requirements for the metathetical exchange of univalent and divalent ionic species.